This invention relates in general to vehicle drum brake assemblies and drum-in-hat disc brake assemblies and in particular to a brake shoe mounting system for use in such a vehicle drum brake assembly and drum-in-hat disc brake assembly.
Most vehicles are equipped with a brake system for slowing or stopping movement of the vehicle in a controlled manner. A typical brake system for an automobile or light truck includes a disc brake assembly for each of the front wheels and either a drum brake assembly or a disc brake assembly for each of the rear wheels. In some instances, the disc brake assembly can be a xe2x80x9cdrum-in-hatxe2x80x9d type of disc brake assembly. The brake assemblies are actuated by hydraulic or pneumatic pressure generated when an operator of the vehicle depresses a brake pedal. The structures of these drum brake assemblies and disc brake assemblies, as well as the actuators therefor, are well known in the art.
A typical drum-in-hat type of disc brake assembly includes a hydraulically or pneumatically actuated disc service brake and a mechanically actuated drum-in-hat parking and emergency brake. The disc service brake includes a rotor which is secured to the wheel of the vehicle for rotation therewith. The rotor includes a pair of opposed friction plates which are selectively engaged by portions of a caliper assembly. The interior of the rotor defines a cylindrical braking surface.
A caliper assembly is slidably supported by pins secured to a mounting flange. The mounting flange is secured to a non-rotatable component of the vehicle, such as the steering knuckle or the axle flange. The caliper assembly includes a pair of brake shoes which are disposed on opposite sides of the rotor. The brake shoes are operatively connected to one or more hydraulically actuated pistons for movement between a non-braking position, wherein they are spaced apart from the opposed friction plates of the rotor, and a braking position, wherein they are moved into frictional engagement with the opposed friction plates of the rotor. When the operator of the vehicle depresses the brake pedal, the piston urges the brake shoes from the non-braking position to the braking position so as to frictionally engage the friction plates of the rotor and thereby slow or stop the rotation of the associated wheel of the vehicle.
The drum-in-hat parking and emergency brake includes a pair of opposed arcuate brake shoes which are supported on a backing plate for selective movement relative thereto. The backing plate is secured to the mounting flange, or alternatively, can be formed integral therewith. Each of the brake shoes has a friction pad or lining secured thereto. The brake shoes extend within the cylindrical braking surface of the rotor. To effect parking and emergency braking action, the operator of the vehicle manually pulls an actuating lever. The lever is connected to an actuation cable having a park brake cable end which, when pulled, actuates a mechanical actuating mechanism. The actuating mechanism is located adjacent one of the ends of the brake shoes and is operative to move the brake shoes outwardly apart from one another such that the friction pads frictionally engage the cylindrical braking surface of the rotor. Such frictional engagement causes slowing or stopping of the rotational movement of the rotor and, therefore, the wheel of the vehicle in a controlled manner.
A typical drum brake assembly includes a backing plate which is secured to a fixed, non-rotatable component of the vehicle, such as the vehicle axle housing. A pair of opposed arcuate brake shoes are supported on the backing plate for selective movement relative thereto. Each of the brake shoes has a friction pad secured thereto. The brake drum assembly further includes a cylindrical brake drum which is secured to the vehicle wheel for rotation therewith. The interior of the brake drum is hollow, defining an inner cylindrical braking surface. The brake drum is disposed adjacent to the backing plate such that the brake shoes extend within the inner cylindrical braking surface. To effect braking action, the brake shoes are moved outwardly apart from one another such that the friction pads frictionally engage the inner cylindrical braking surface of the brake drum. Such frictional engagement causes slowing or stopping of the rotational movement of the brake drum and, therefore, the wheel of the vehicle in a controlled manner.
One or more actuating mechanisms are provided in the brake drum assembly for selectively moving the brake shoes outwardly apart from one another into frictional engagement with the cylindrical braking surface of the brake drum. Usually, a hydraulically or pneumatically actuated service brake mechanism is provided for selectively actuating the drum brake assembly under normal operating conditions. Such a service brake mechanism can include a hydraulic cylinder having a pair of opposed pistons which abut and move the brake shoes apart from one another into frictional engagement with the cylindrical braking surface of the brake drum.
A mechanically actuated parking and emergency brake mechanism is also usually provided for selectively actuating the drum brake assembly. The parking and service brake mechanism can include an actuating lever pivotally supported on one of the brake shoes. The actuating lever is connected to a cable which, when pulled, moves the brake shoes apart from one another into frictional engagement with the cylindrical braking surface of the brake drum.
This invention relates to a brake shoe mounting system for a vehicle brake assembly. The vehicle brake assembly brake shoe mounting system includes a an brake mounting member and a pair of brake shoes slidably supported relative to the brake mounting member. The brake member is adapted to be secured to a fixed, non-rotatable component of the vehicle and includes an abutment having a pair of opposed slots formed therein. Each brake shoe includes a first end, an opposite second end, a web portion, a rim portion secured to an outer surface of the web portion, a friction pad secured to an outer surface of the rim portion, and only two shoe slides provided on at least one side of the rim portion. One of the two shoe slides is provided near the first end of the brake shoe and the other of the two shoe slides is provided generally intermediate the first and second ends of the brake shoe. In accordance with this invention, the second end of the brake shoe defines a shoe abutment end. The shoe abutment end is disposed in the slot of the abutment and in contact with an associated surface of the slot of the abutment to thereby define a third shoe slide of the brake shoe.